September 21st, 2011

More Data but No Answers About Platelet Function Testing

The RECLOSE 2–ACS (Responsiveness to Clopidogrel and Stent Thrombosis 2–ACS) trial from Italy provides new information about platelet reactivity but doesn’t answer any of the key questions about the possible role of platelet function testing in clinical practice.

In a paper published in JAMA, Guido Parodi and colleagues report on 1,789 ACS patients who underwent PCI and who had their platelet reactivity measured. Patients found to have high residual platelet reactivity (HRPR) received a larger dose of clopidogrel or were switched to ticlopidine.

  • After 2 years’ follow-up, the rate of cardiac death, MI, urgent coronary revascularization, or stroke was 14.6% in the group with HRPR versus 8.7% in the group with low residual platelet reactivity (absolute risk increase: 5.9%; CI 1.6%-11.1%, p=0.003).
  • Within the HRPR group, there was no difference in outcome between patients who, after treatment, had an ADP test result below 70% and those with an ADP result of 70% or above.
  • Stent thrombosis occurred in 6.1% of patients with HRPR versus 2.9% of those with low residual platelet reactivity (absolute risk increase: 3.2%, CI 0.4%-6.7%; p=0.01).

In an accompanying editorial, Dominick Angiolillo writes that the absence of benefit on the primary endpoint with adjusted therapies “leaves unsolved the pivotal dilemma of whether platelet reactivity is simply a marker of risk or if it is a modifiable risk factor that can affect prognosis.” Platelet function testing, says Angiolillo, remains a research tool: “Currently available evidence cannot support routine use of PFT in clinical practice.”

2 Responses to “More Data but No Answers About Platelet Function Testing”

  1. What price reactivity?

  2. Joseph Minadeo, M.D. says:

    A 2.9% incidence of stent thrombosis in patients with low residual platelet reactivity seems high.